Institut für Organische Chemie und Biochemie, Freiburg Institute for Advanced Studies (FRIAS), Universität Freiburg, Albertstr. 21, Germany.
Chemistry. 2011 Oct 10;17(42):11780-8. doi: 10.1002/chem.201100843. Epub 2011 Sep 2.
New methodology for the stereoselective synthesis of trisubstituted olefins is presented. The use of ortho-diphenylphosphanyl benzoate (o-DPPB) as a directing leaving group for copper-mediated allylic substitution with Grignard reagents allowed for the stereoselective construction of a wide range of E olefins, without the need for an adjacent electron-withdrawing group. Our modular three-step approach toward trisubstituted alkenes commenced with geminal α-methylene aldehydes. Addition of an organometallic reagent and introduction of the o-DPPB group by esterification was followed by the o-DPPB-directed copper-mediated allylic substitution with a Grignard reagent to furnish stereodefined trisubstituted olefins. Additionally, incorporation of a stereocenter from the chiral pool allowed the preparation of an enantiomerically pure olefin that bore three alkyl substituents in high E/Z selectivity.
本文提出了一种立体选择性合成三取代烯烃的新方法。使用邻二苯基膦基苯甲酸酯（o-DPPB）作为导向离去基团，通过铜介导的与格氏试剂的烯丙基取代反应，可以立体选择性地构建广泛的 E 型烯烃，而不需要相邻的吸电子基团。我们的三取代烯烃模块化三步法从偕二甲基亚甲基醛开始。首先加成一个有机金属试剂，并通过酯化引入 o-DPPB 基团，然后进行 o-DPPB 导向的铜介导的与格氏试剂的烯丙基取代反应，得到立体定义明确的三取代烯烃。此外，从手性池中引入一个立体中心可以制备出对映体纯的烯烃，该烯烃以高 E/Z 选择性带有三个烷基取代基。
